Biofeedback

definition of biofeedback

the use of electronic instrumentation to provide objective information to an individual about physical function or response

types of biofeedback

force plates, EEG, BP, HR, EMG

steps for how feedback is normally given in the clinic

identify task to pt, give verbal feedback and motivation → pt does the task → evaluate with visual inspection and palpation → respond with verbal cues or feedback

how does biofeedback improve the feedback process for the patient

better regulation of muscle activation through EMG feedback

how does biofeedback improve the feedback process for the therapist

allows them to better alter parameters to make exercises more/less difficult and target specific muscles

advantages of EMG biofeedback

speed, continuity, sensitivity, objectivity

contraindications for biofeedback

none because nothing is coming out of the electrodes

requirements to benefit from EMG biofeedback

potential for improvement, at least a trace contraction of volitional activation, cognition

characteristics of larger interelectrode distance

greater volume of muscle monitored, larger signal, more crosstalk

characteristics of smaller interelectrode distance

smaller volume of muscle monitored, greater specificity

normal interelectrode distance

2-3 cm

what does the EMG unit record

the voltage change as it crosses the leads (mostly muscle but some neurons involved)

EMG amplitude reflects

size and number of motor units, interelectrode distance, distance from electrodes

relationship between interelectrode distance and amplitude seen on EMG

larger interelectrode distance causes a larger amplitude

things than contaminate an EMG signal

crosstalk, movement artifact, electrical noise, attenuation (insulation from skin/fat)

steps for EMG signal processing

amplification → rectification → filtering

function of amplifying an EMG signal

to distinguish muscle activity from electrical noise to improve the accuracy of the reading

function of rectifying an EMG signal

flip from negative to positive to see the total muscle activity

function of filtering an EMG signal

take an average to smooth out the signal

other factors needed to translate EMG into muscle force

fatigue, SEC, length-tension relationship, electrode placement, day-to-day variance

placement of biofeedback sensor

over motor point of a muscle belly, pt positioned in task specific posture

how to decide an EMG threshold

find the amplitude at a patient’s max activation then take a percentage of that

what is threshold selection dependent on

specific level of activity (over or underactivity), feedback on or off

types of feedback given

audio or visual

long term goals of EMG biofeedback

increase recruitment in a hypoactive muscle, relax a hyperactive muscle

short term goals of EMG biofeedback

progression than includes weaning, patient education

how to decrease muscle activity with biofeedback

incorporate relaxation techniques, keep lowering the threshold to make it harder